The goal of the project is to identify from among compounds exhibiting activity in the signal transduction target screens in Projects 2, 3 and 4 those compounds that have significant growth inhibitory activity against tumor cells in vitro. A panel of 7 human tumor cell lines will be studied including three colon cell lines to represent one of the most chemoresistant human solid tumor types, and two leukemia cell lines representing a generally chemoresponsive human tumor type. The panel of cell lines includes all the human tumor xenografts used in the in vivo antitumor activity screen. Growth inhibitory activity will be measured using the soft agar colony formation assay. This assay is readily amenable to automation with high sample throughput, it is highly reproducible and gives a direct measure of cell growth with time. Statistical analysis of growth indices will be used to compare the effects of the agents among different cell lines. Agents exhibiting significant activity against any of the cell lines will be candidates for in vivo antitumor activity testing against the same cell lines and other human tumors in Project 6. Secondary studies will be conducted on agents showing only a partial in vivo response to identify pharmacodynamic and pharmacokinetic reasons for the discrepancy in activity. The information derived will be used by Project 1 to help design more active analogues of the compounds, for example with more desirable pharmacokinetic properties.